In the “hands-on” cooperative robot control paradigm, both the operator and the robot hold the tool while the forces exerted by the operator on the tool are sensed with a force/torque sensor and the robot moves to minimize these forces, effectively rendering the operator's desired motion. For surgical applications, quick tool changes are desirable and often required for timing and safety reasons. Specifically, unintended patient movement requires an immediate compensatory repositioning of the instrument to avoid tissue injury.
A quick tool exchange mechanism is desirable for a surgical system based on cooperatively controlled robot where frequent insertion and removal of surgical instruments is required, e.g., Vitreoretinal surgery. For safety reasons, this tool interface should also provide a very quick and robust instrument removal from the surgical site that is not dependent on a functioning robot. While engaged, this mechanism should not impede the function of the robot or the ability of the surgeon to perform desired tasks.
One approach to this problem is to use a simple d-tenting mechanism in which a small spring-loaded ball or pin in the tool holder engages a socket or groove on the tool shaft to hold the tool in place unless a sufficiently large force is exerted to disengage the tool. Another approach is to use a magnet. One challenge with these approaches is holding the tool firmly enough to permit the operator to guide the tool without unintended break-away while also ensuring that the required release force is not so large that the tool cannot be removed very quickly and safely if the need arises. This challenge is especially crucial in applications such as retinal microsurgery, where the forces are extremely delicate and the need for very quick, non-disruptive tool withdrawal is great.
Accordingly, there is a need in the art for a system and method for assisting with tool exchange during surgery.